For many years size applicators, commonly referred to as size boxes, have normally included an immersion roll at the entrance end to immediately guide the sheet of yarns downwardly in free flight into the size solution and then upwardly out of the size solution and through one or more pairs of squeeze rolls. The speed of operation of this type of size box has been limited because the yarn is exposed to the size solution for a very short period of time and the parallel yarns tend to become lapped over each other or laced together when they are passed through the size box at high speed.
In an attempt to increase the speeds at which textile yarns could be sized, size boxes with different immersion and squeeze roll arrangements were developed. Examples of size boxes with various types of immersion and squeeze roll arrangements are illustrated in U.S. Pat. Nos. 2,849,784; 2,862,280; 2,884,893; 3,067,061; and 3,284,870. The size boxes of these prior art patents do permit the yarns to be sized at increased speeds because they provide increased exposure of the yarn to the size solution so that the size solution can penetrate into the yarn. This increased penetration of the size requires that increased squeezing pressure be applied by the pressure rolls to remove the desired amount of size from the yarns. However, as nip pressures between the squeeze rolls are increased, the medial portions of the pressure rolls are subjected to deflection or bowing so that the yarns on the outer side portions of the yarn sheets are subjected to greater squeezing pressure than those yarns in the medial portion of the yarn sheet. Also, it is difficult to accurately control and coordinate the rotational speed of the various immersion and squeeze rolls in the size box to maintain the yarns under uniform tension throughout the path of travel through the size box.